Also realize there is a difference between mature content and pornography. The latter is not allowed there but outside of a sexfight artist, i can't see much that a female fight artist might run afoul there. But all of it will likely be labelled mature content (because it depicts violence) and mature content tends to be not accessible to a non member. But anyone can become a member.i am and I can't draw a damn thing. And if you can't see much in that link I posted, well become a member 
The short version : DA doesn't allow sexual intercourse, erections, sex toys or minors in provocative positions to be displayed. (If you are wanting to do the last one, you aren't too welcome at FCF either)
I don't go to Deviant Art pages because ever so often I get told that this or that picture is censored. I don't bother anymore. So if you're an artist and you want to share your work you have to think about the best way to do it. I don't think Deviant Art is the place for it. And please don't bring child pornography into the discussion. I don't think anyone here is into that or wants to go there
1. Do you have an alternative to DA in mind? It is one thing to go "Me no like", quite another to have a suggestion where else these artists should go. Plenty of artists have done fine there, so what would you suggest?
2. As stated, if you aren't logged into DA, you don't see mature content. Lots of sites do this. Many artists there willingly put that label on their work to save themselves and the site grief. Some artists would like only adults to see their work. That is why the mature content filter on that site is ON for non members. Saves them getting a letter from some angry parent whose 10 year old saw a naked person. If you wish to see everything on that site, log in. It is not exactly a tough thing to do. If that is too much work for you then fine, but don't make the site sound like it is filled with pictures no one can see.
For example this
http://k9joe.deviantart.com/art/Topless-65090020 has a mature filter on. But i see it when logged on my account (where I have the filter turned off).
3. Don't make false accusations. I quoted the rules of a site so artists don't falsely think that site hates nudity or all eroticism. Hardly bringing a subject into the discussion. Forgive me for assuming members of this site are capable of receiving information.
